1. Field of the Invention
The present invention relates to a golf ball having a specific coating layer at its surface portion, which allows dimples to be precisely shaped and sharp edged and which can be given sufficient durability and functions to improve travel properties, spin properties, and feel on impact. This invention also relates to a production process thereof.
2. Related Art
Two-piece golf balls, three-piece golf balls, and thread-wound golf balls are usually produced by a process which comprises enclosing a solid core or a thread-wound core with a cover material and forming dimples by compression or injection molding, applying a coating on the surface of the cover material, conducting mark stamping by a transfer printing method, and then forming an outermost layer coating of the ball. In some cases, the mark stamp may be directly applied to the cover material surface, and then an outermost layer coating may be formed. One-piece golf balls are produced by a process which comprises preparing a solid core having dimples by compression or injection molding, and then subjecting the solid core to mark stamping and application of an outermost layer coating of the ball in this order.
In this case, the coating on the surface of the cover material and the outermost layer coating of the ball use a thermosetting coating material or a two-pack system coating material. Since coatings formed of these coating materials cannot be easily deformed by the application of heat and pressure, dimples cannot be easily formed after formation of such coatings. Therefore, the coating step is performed after dimples are formed.
However, the above-described conventional coating formed on the cover material or outermost layer coating of a ball is formed to protect the golf ball from dirt or scratches and to improve the appearance thereof. No attempts have been made to give these coatings functions to improve travel properties, spin properties, and feel on impact.
By contrast, the present inventors approached an idea to give a coating at a ball surface portion functions to improve travel properties, spin properties, and feel on impact of a golf ball. In order to give the coating such functions, the coating must accordingly be made thicker. At the same time, the coating must have sufficient durability to maintain the functions.
However, when the coating step is performed after formation of dimples as conventionally practiced, the coating shallows the dimples and dulls dimple edges if formed relatively thick on dimples. This impairs preciseness of a dimple shape. Accordingly, coating thickness must be made as thin as possible in order to prevent the coating from impairing preciseness of the dimple shape. Thus, it is difficult for a coating to have a thickness such as to have sufficient durability and functions to improve travel properties, spin properties, and feel on impact.